Helmet clock



FIG. 1 is a perspective view of a helmet clock showing our new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a left side elevation view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines in FIGS. 3 and 7 represent an unclaimed boundary, the area within which forms no part of the claimed design. 

CLAIM The ornamental design for a helmet clock, as shown and described. 